The present invention is directed to a composite papermaking fabric which is preferably used in the forming section but could also be used in the dryer section. The term composite fabric refers to a fabric comprising two woven structures one of which is the paper side fabric or upper fabric and the other of which is the machine side fabric or lower fabric. The paper side fabric includes a support surface which surface receives and supports the paper forming pulp during the paper forming operation. The lower or contact fabric separates the support fabric from the machine rollers during the paper forming operation and includes a roller contact or contact surface. Both fabrics must be stable and provide the required drainage. The support fabric must also provide an even support surface without unduly high knuckles or unduly deep knuckle depressions so as to not mark the paper during the paper forming operation.
The upper and lower fabrics are bound together with a binder yarn which in the instant case comprises fabric born or intrinsic warp yarns. The terms fabric born or intrinsic warp yarn indicates that the binder yarn while binding the upper and lower fabrics together also weaves in the machine direction with and is an integral part of the weave pattern of both the upper and lower fabrics. The term warp yam refers to yarns which weave in a single specified layer of the fabric and in the machine direction. The term weft yarn refers to yarns woven transverse of the warp yarns.
Composite papermaking fabrics are well known as are illustrated by the U.S. Pat. Nos. 5,152,326; 5,826,627; 6,202,705; and 6,240,973.
It is an object of the present invention to provide a composite papermaking fabric which provides uniform drainage, a smooth and even support surface and extended wear.
Another object of the invention is a papermaking fabric in which the support surface is formed in a one up, one down weave pattern.
Another object of the invention is a composite papermaking fabric in which fabric born or intrinsic warp yarns bind the upper and lower fabrics together and weave with weft yarns to form the lower fabric.
Another object of the invention is a composite papermaking fabric in which the weft yarn of the upper fabric at the binding points are supported against downward movement.
Another object of the invention is the provision of a composite papermaking fabric in which no pairing of weft yarns appear on either surface.
Another object of the invention is the provision of a composite papermaking fabric in which no pairing of warp and fabric born or intrinsic warp yarns appear on either surface.